Barrel and gas duct assembly means for semi-automatic firearms



June 6, 1967 T. LOFF'LER 3,323,418

BARREL AND GAS DUCT ASSEMBLY MEANS FOR SEMI-AUTOMATIC FIREARMS Filed Oct. 26, 1965 United States Patent 3,323,418 BARREL AND GAS DUCT ASSEMBLY MEANS FOR SEMI-AUTOMATIC FIREARMS Theodor Liilller, Mullheim, Baden, Germany, assignor to Rheinmetall G.m.b.H., Dusseldorf, Germany, a German company Filed Oct. 26, 1965, Ser. No. 505,265 Claims priority, application Germany, Oct. 29, 1964, R 39,131

5 Claims. (Cl. 89-191) ABSTRACT OF THE DISCLOSURE A readily removable gas duct providing operative communication between a firearm barrel and a gas cylinder facilitates ready interchangeability of barrels for a gasoperated automatic firearm.

This invention relates to gas-operated automatic firearms having a gas cylinder being connected to a tapping or bleeder hole in the barrel of the Weapon by way of a duct such as a tube.

It is an object of this invention to permit changing the barrel of gas-operated automatic firearms in a particularly simple and time-saving manner, and, if required, Without requiring the attention of an armourer. This invention also permits the exchanging of an exisiting barrel for a shorter one or for a barrel of larger cross-section and therefore of greater thermal capacity. Such needs arise. for example, when a basic assembly group intended as a nucleus for a group of weapons is to be converted as desired into a light or heavy machine gun, an assault rifle or a machine pistol. In all these cases, the object is to create a so-called group of firearms based on the basic assembly group of components, in such manner that the elementary construction is substantially retained in all the versions of the group of firearms and is completed in each instance by means of attachments to form a desired type of firearm within the group.

According to the present invention, the gas duct between the barrel of the firearm and the gas cylinder mounted on the firearm casing is designed so that it can be disconnected easily. More particularly, one of the disconnecting surfaces, namely that associated With the barrel of the firearm, is arranged on a supporting member fixed to the barrel in the region of the tapping hole, while the other disconnecting surface is connected to the gas cylinder. The disconnecting surfaces incorporate the sealing surfaces at the point of interruption of the gas duct.

In accordance with a subsidary feature of this invention, the disconnecting and sealing surfaces are so formed that the relative movements occurring between the disconnecting surfaces when the firearm is used, for exarnple through heating due to use or the influences of ambient temperature changes, have no perceptible effect on the gas-tightness of the joint. To this end, the sealing surfaces are so designed that they consist of a cone on the one hand and a funnel on the other hand, the cone and the funnel being so sprung in relation to one another that they remain in contact with a sealing action even on axial displacement. As a rule, it will be sulficient to spring-load either the cone or the funnel; in exceptional cases, however, the spring-loading of both elements of the seal, i.e. both disconnecting surfaces, might be expedient. In order to improve the sealing effect, the sealing surfaces may be provided with grooves, slots or the like, which then become operative as labyrinth seals.

According to another subsidiary feature of the invention and in order to provide a particularly favorable construction for the point of disconnection associated with the barrel of the firearm, the point of disconnection is provided in the region of the front sight assembly. It is also advantageous to effect a deflection of the gas stream which has as low a loss as possible from the point of view of fluid mechanics, for example an arcuate deflection, between the tapping hole in the barrel and the point of disconnection. An intermediate piece mounted in the front sight assembly and arranged coaxially with the gas cylinder is provided for this deflection.

Some of the objects and advantages of the invention having been stated, others will appear as the description proceeds when taken in connection with the accompanying drawings, in which:

FIGURE 1 is an elevational view, partly in section, of a forward end portion of an assault rifle constructed in accordance with this invention;

FIGURE 2 is a section along the line A, B, C, D in FIGURE 1; and

FIGURE 3 is a view from below, partly in section of the parts adjacent the cocking slide of the breech mechanism and its guide sleeve, as seen substantially in the direction of the arrow E in FIGURE 1.

Referring now more particularly to the drawing, a firearm is there shown, which has a casing 1 in which a barrel 2 is fixed. On the barrel 2 is mounted a front sight assembly indicated generally at 3 and containing a gas duct 4, in which the deflection of the stream of gas tapped from the barrel is effected by an intermediate piece 5. The deflection is produced by a substantially arcuate milled recess 6 in the intermediate piece 5. The latter is fixed to the front sight assembly by means of a pin 7. Arranged concentrically with the intermediate piece 5 is a sleeve-shaped body 8 having a flange 9 with locking bores 10 for cooperation with a spring-loaded pin 11 guided slidably in the body of the front sight assembly. In the plane of the tapping hole 12 in the firearm barrel, the body 8 has a plurality of nozzle-like bores 13, 14, 15 which are of different transverse cross-sectional area and permit adjustment of the quantity of gas to be supplied to a gas cylinder, which will be described hereinafter. This adjustment is effected by turning the body 8 after the pin 11 has first been forced in against the action of a spring 11. This can be done, for instance, with the bullet tip of a cartridge, which is pressed against a center punch hole 16 in the pin 11.

A cylindrical head piece 17 of a gas feed tube 18, having an insertion end 19 which is in the form of a cone or small cone angle, is mounted in the sleeve part 8 so that it is capable of axial movement. Consequently, by simply pushing this insertion end in, it can be connected in substantially gas-tight fashion with the head piece of a gas cylinder 20, which is itself fixed, as by Welding at 21 and 22, to the casing 1 of the firearm and to a tube 23 mounted on the casing of the firearm.

The gas piston 24 of the firearm is guided slidably in this gas cylinder, and forms an extension of a buffer cylinder 25. The latter serves, in conjunction with a damping piston (not shown) mounted at the front end of the breech mechanism carrier, to resiliently absorb surplus energy transmitted to the breech mechanism carrier on firing.

As will readily be seen, as a result of the assembly of the gas piston at the front end of the buffer cylinder, 21 particularly neat solution is obtained from the point of view of design for the conversion of an existing firearm of the type identified as a gas-operated rifle having a semirigid locking bolt. At the same time it is also important that the gas cylinder 20 is so designed (see in particular FIGURE 1) that there is suflicient space available in its middle portion for accommodating the sleeve 26 of the cocking slide 27, which has a pivot bearing 28 and a locking device 29 for the two locations of the cocking slide.

Considered as a whole, the above-described construction of a firearm makes possible the disconnecting of the barrel 2, with the front sight assembly 3 and the parts mounted on that assembly, including the locking sleeve 8, rapidly and simply from the other parts of the firearm, that is from the gas cylinder, in the region of the gas duct. For this purpose it is only necessary to disengage the barrel from the locking piece, as for example, by undoing a retaining nut, and then draw it off forwardly in the direction of its longitudinal axis. The point of disconnection of the gas duct may be located either be tween the group consisting of the sleeve 8 and the head piece 17 of the gas feed tube or between the assembly consisting of the insertion end 19 of the gas tube and the head piece of the gas cylinder 20. At both points of disconnection the cooperating parts are able to perform certain relative movements with respect to one another, such as may occur during use of the firearm, for example as a result of the effect of temperature without loss of gas-tight sealing.

The insertion of another, for example shorter, barrel (for instance for machine pistols) or a barrel of greater wall thickness (for example for machine guns), is easily accomplished in that the procedure is merely reversed. It is also possible to first couple the barrel with the locking piece by means of a bayonet point and then to couple the point of disconnection of the gas duct at the end of this turning movement of the barrel.

In the drawings and specification there have been set forth preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and discriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claims.

What is claimed is:

1. In a gas operated semi-automatic firearm having a barrel, a firearm casing, and a gas operation cylinder supported in said casing and defining an axial bore, means for communicatively connecting the barrel and cylinder for the transmission of projectile propellant gases from the barrel to the cylinder upon firing of the firearm com prising a front sight assembly on the barrel and including a gas passage communicating with the barrel and defining an axial bore substantially aligned with the cylinder bore and a tube member extending between said front sight assembly and the cylinder and slidably and removably received with the aligned bores for communicating with said gas passage and the cylinder.

2. A firearm as claimed in claim 1 wherein said tube member has sealing surfaces engaging said bores to maintain a relatively gas-tight seal therebetween upon relative axial displacement of said front sight assembly and the cylinder.

3. A firearm as claimed in claim 1 wherein said bore formed in the cylinder and the cooperating end of said tube member have conically tapered sealing surfaces.

4. A firearm as claimed in claim 1 wherein said front sight assembly includes a means for deflecting gases from the barrel into said tube at low fluid pressure losses.

5. A firearm as claimed in claim 4 wherein said means for deflecting gases comprises an intermediate piece anchored in said front sight assembly and having an arcuate surface therein.

References Cited UNITED STATES PATENTS 2,186,582 1/1940 Gebauer 89-193 2,462,119 2/1949 Moore 89-193 2,865,256 12/1958 Marsh 89--191 3,180,226 4/1965 Lichhead 89--191 3,225,657 12/1965 Kruzell 89-191 X FOREIGN PATENTS 560,866 4/1944 Great Britain.

OTHER REFERENCES BENJAMIN A. BOROHELT, Primiary Examiner.

0 S. C. BENTLEY, Assistant Examiner. 

1. IN A GAS OPERATED SEMI-AUTOMATIC FIREARM HAVING A BARREL, A FIREARM CASING, AND A GAS OPERATION CYLINDER SUPPORTED IN SAID CASING AND DEFINING AN AXIAL BORE, MEANS FOR COMMUNICATIVELY CONNECTING THE BARREL AND CYLINDER FOR THE TRANSMISSION OF PROJECTILE PROPELLANT GASES FROM THE BARREL TO THE CYLINDER UPON FIRING OF THE FIREARM COMPRISING A FRONT SIGHT ASSEMBLY ON THE BARREL AND INCLUDING A GAS PASSAGE COMMUNICATING WITH THE BARREL AND DEFINING AN AXIAL BORE SUBSTANTIALLY ALIGNED WITH THE CYLINDER BORE AND A TUBE MEMBER EXTENDING BETWEEN SAID FRONT SIGHT ASSEMBLY AND THE CYLINDER AND SLIDABLY AND REMOVABLY RECEIVED WITH THE ALIGNED BORES FOR COMMUNICATING WITH SAID GAS PASSAGE AND THE CYLINDER. 